From what I've heard and seen the quality of metal makes them prone to breaking, and you need skill to take full advantage of the razor sharp edge. I have seen a great video showing katana students cutting bamboo and struggling and then a master going clean through that I wish I could have found again. For the record I don't think they are shit swords, just they look really cool and that has lead to various media elevating their superiority to other swords beyond reality.